1. Field of the Invention
The present invention relates generally to various chemical and/or mechanical processes for the deagglomeration, disaggregation and/or grinding of various materials, in particular, the present invention relates to the chemical-mechanical deagglomeration and/or disaggregation of specified materials, which results in the separation of clustered particles of specified materials, such as ultra-dispersed diamond (UDD), ultra-nano crystalline diamond (UNCD), various carbon materials, including coal and the like, and other aggregated and/or agglomerated ultra-fine powders, such as single metal oxides, complex metal oxides, coated powders and the like.
2. Description of Related Art
Powdered material, fine particulate material, micrometer-sized particles, nanometer-sized particles and similar materials are now being used in a variety of specialty applications. For example, such materials are used in precision polishing processes, chemical mechanical planarization (CMP), fuel cell applications, oxygen generation, biotechnology processes, petrochemical processes, chemical processes, transportation applications, performance material sectors, etc. However, in order to be useful in these specialty applications, such powders need to be refined and provided in usable forms, such that end-use manufacturers are able to obtain high quality powders at a reasonable cost. Accordingly, there is a need for a process capable of providing such materials to manufacturers in various industries, including electronics, energy generation, environmental control, petrochemical and chemical industries.
As discussed, due to the application in such specialized industries, greater process performances are required to meet tighter specifications and satisfy the increasing demands of high quality powders. Attaining such tight specifications requires improving the control over the particle material properties. Dependent upon the type of materials to be produced, each has various drawbacks and requires the production of pure powdered particulate matter. For example, some of these materials may include UDD, UNCD, carbon materials, coal, single oxide powders, complex metal oxide powders, coated particles, etc.
All of these small-particulate materials tend to form aggregates, agglomerates and/or flocculates during the manufacturing process. Specifically, either during the formation process and/or during subsequent processing, aggregates or clusters form, which are composed of individual particles held together by relatively weak bonds, causing a cohesive force and formation of such clusters. In order to maximize the physical and chemical characteristics of these powders, it is desirable to overcome these cohesive forces, which results in discrete particulates and/or reduced cluster sizes.
Single metal oxides have a wide range of industrial applications, including use as a polishing material, a catalyst support material, pigment, ultraviolet blocker, etc. Non-mined ceramic powders are typically prepared by isolating the metal of interest as a compound or metal, and then reacting to the material to form the desired compound. For the production of aluminum oxide, one typically used process is the “BAYER” process, where aluminum is separated to the compound aluminum hydroxide through a digestion and precipitation step performed on gibbsite. The aluminum hydroxide is then heated to 1050° C. to decompose the hydroxyl ions and form Al2O3 and H2O. A final step in this process is the grinding of the Al2O3 to obtain the desired particle size. Further, Al2O3 can be prepared as either transition alumina or alpha alumina, which are differentiated by crystalline structure. The high surface areas and a lower hardness of the transition alumina are utilized in the catalyst and polishing of semiconductors. One drawback of the above-described method for the production of single metal oxide powders is the requirement for reducing the particle size through a milling step. Additional technical barriers associated with this process include a minimum size limit to which particles can effectively be reduced (approximately 500 nm), a broad particle size distribution and a substantial energy and equipment requirement for milling.
With respect to complex metal oxides, which is an oxide compound containing more than one metal, such compounds (e.g., BaTiO3) and solid solutions include a metal oxide uniformly dispersed through a structure of another oxide, such as Y2O3 stabilized ZrO2 (YSZ). Currently, complex metal oxides and solid solutions of metal oxides are produced through solid state reactions, crystallization of melts and solution methods.
In the solid state reaction methods, compounds containing the metals of interest are combined, thoroughly mixed and then fired. During the firing process, the precursor compounds break down into the oxides of the individual metals. The metal ions then diffuse together to produce the compound containing both metals. This diffusion process tends to be slow, and therefore, the material is cooled and re-ground to create fresh surfaces for the individual metal oxides to interact, and produce more of the desired compound during subsequent re-firing. This cooling, grinding and re-firing process may be repeated three or four times to achieve the desired level of homogeneity and conversion to the final product. Some primary technical limitations of this process include the formation of secondary phases, incomplete reaction of the precursor materials, the growth of large particles and agglomerates during the extended firing process and the high energy requirements for re-firing the material and grinding. An additional deficiency is the limit on the minimal particle size from the milling process.
One method of overcoming such limitations with the solid state reaction method of producing complex metal oxides is through wet chemistry methods. In these methods, compounds containing the metals of interest are dissolved in a solution, the water quickly removed from the solution (or the solution is gelled), and the resulting solid or gel is heated. Combining the metal ions in a solution provides a method for intimately mixing the different metal ions on an atomic level. Quickly removing the water or gelling solution stabilizes the high degree of mixing between the metal ions achieved in the solution. The heating of the de-watered solution or gel in the presence of oxygen results in the formation of oxide compounds. Such wet chemistry methods, while successful in a laboratory, appear to be difficult to scale up to a pilot level operation, which is an obvious technical limitation. Additionally, there are difficulties with obtaining the resource materials exhibiting consistent properties utilizing these methods. Some manufacturers are no longer involved in the production of such materials due to these difficulties.
One variation of the wet chemistry method is the flame-spray method of producing oxides. In this method, the solution prepared is atomized and passed through a flame. When the droplets pass through the flame, the liquid in the solution is rapidly vaporized and the reactions to convert the dried substance to an oxide occur. In flame spray technologies, particle size control limitations arise from variations in the time-temperature history encountered as the particles pass through the flame. An additional concern with the flame spray technology is that as the particles pass through the high temperature regions of the flame, the oxides may be preferentially volatilized leading to the segregation of the metal ions. This potentially results in not obtaining the desired composition in the final product, and in a non-uniform chemical composition throughout this final product.
Another type of material in this general application is referred to as coated particles. Coated particles may be made when a coating oxide/material wets the oxide surface of the primary particle. For example, the catalytic behavior of V2O5 when applied to TiO2 for alcohol conversion to aldehydes is greatly improved through coating the V2O5 onto the surface of TiO2. Coated particles are produced through a wet insipient process. In the wet insipient process, particles are saturated with a solution containing the metal of interest. The powder is then dried and heat-treated to convert the metal by the oxide or metal and solution, such that the solution oxide/metal will form a continuous coating on the particle surface. Some technical barriers associated with these coated particles are the requirement of a two-step process, as well as the potential for the coating to bridge between the particles, thereby forming agglomerates. In addition, this two-step process leads to an effective doubling of the energy required to produce the final particles.
Ultra-Dispersed Diamond (UDD) or Ultra-Nano Crystalline Diamond (UNCD) are the synthetic diamonds found by the detonation synthesis method resulting in a relatively narrow size distribution, which is also characteristic of diamond particles found in meteorites and protoplanetary nebulae. UDD or Nano Diamonds, also known as nanocrystalline diamonds, have been commercially available for many years. Applications for these materials include, but are not limited to: electrodeposition, polymer composition, films and membranes, radiation and ozone-resistant coatings, lubricating oils, greases and lubricating coolants, abrasive tools, polishing pastes and polishing suspensions for hard-disk drives, optical, semi-conductor component, chemical mechanical planarization, etc. Due to the UDD's biocompatibility, these materials have potential uses in a variety of biological and medical applications. Additional areas of application include fuel cells, magnetic recording systems, catalysts, sintering, advanced material composites, new materials, etc.
Another type of material contemplated by the present application is anthracite or coal. Coal is composed of a complex, heterogeneous mixture of organic and inorganic components that vary in shape, size and composition depending upon the nature of the vegetation from which they were derived, the environment in which they were deposited and the chemical and physical processes that occurred after burial. Finely sized or polarized anthracite and other coals are being used in fuel and non-fuel applications, including applications that use these coal materials as pre-cursor particles for the production of high value added carbon products. These carbon products, however, have minimal or no requirements directed to the exact physical and chemical properties, such as: particle size, particle distribution, particle shape, specific surface area, and bulk purity. Many of these application needs have been met with little or no success according to the prior art.
Normally, such ultra-fine powders, including UDD, during production or processing, form aggregate/agglomerates, commonly referred to as “clusters”. In particular, either during the formation process and/or subsequent processing steps, aggregates form, made up of individual particles held together by relatively weak bonds or material bridging, as discussed above. In order to maximize the nano diamonds and other nano-sized particles potential in the aforementioned applications, one must overcome these cohesive forces resulting in discrete particulates or reduced cluster sizes. In processing of micrometer-sized and nanometer-sized coal particles, this is commonly referred to as particle accretion.